The centre-backs have both committed their long-term futures to Brendan Rodgers' side and Reina thinks they can become as good as Champions League-winning pair Sami Hyypia and Jamie Carragher.
"I don't see any reason why they can't do the same as Carra and Sami did, though they were one of the greatest centre-back couples this club has ever had," Reina told the club’s official website.
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"The understanding between them is great and they've been really solid lately. In the last year and a half or so they have been brilliant for us.
"It's great for the club and I'm happy for them that they've got new deals."
Both Skrtel and Agger are 27-years-old and Reina is eyeing several years behind the pair, who have just signed new contracts with the Reds.
He added: "If I am not mistaken they are similar ages to each other, so they have five or six years still to play their best football.
"It's good they've signed contracts because it's a fact that they are one of the best centre-back couples in the Premier League."